import java.util.Scanner;

public class program16{
    public static void main(String[] args) {
        Scanner in = new Scanner(System.in);
        System.out.print("Enter the side: ");
        double s = in.nextDouble();
        double area = 3 * Math.sqrt(3) / 2 * s * s;
        System.out.printf("The area of the hexagon is %.4f%n", area);
    }
}